Catalyst and a method for manufacturing the same

ABSTRACT

An improved platinum and method for manufacturing the improved platinum wherein the platinum having a fractal surface coating of platinum, platinum gray, with a increase in surface area of at least 5 times when compared to shiny platinum of the same geometry and also having improved resistance to physical stress when compared to platinum black having the same surface area. The process of electroplating the surface coating of platinum gray comprising plating at a moderate rate, for example at a rate that is faster than the rate necessary to produce shiny platinum and that is less than the rate necessary to produce platinum black. Platinum gray is applied to manufacture a fuel cell and a catalyst.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation in part of application Ser. No.11/198,361, “Platinum Surface Coating and Method for Manufacturing theSame”, filed Aug. 4, 2005, the disclosure of which is incorporatedherein by reference, which is a divisional of application Ser. No.10/226,976, “Platinum Electrode and Method for Manufacturing the Same”filed Aug. 23, 2002, the disclosure of which is incorporated herein byreference, which claims the benefit of U.S. Provisional Application No.60/372,062, “Platinum Deposition for Electrodes”, filed Apr. 11, 2002,the disclosure of which is incorporated herein by reference.

FEDERALLY SPONSORED RESEARCH

This invention was made with government support under grant No.R24EY12893-01, awarded by the National Institutes of Health. TheGovernment has certain rights in the invention.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The field of the invention relates to a catalyst especially for a fuelcell and autocatalyst and electrode surface coating and electroplatingprocesses for deposition of surface coating, especially in a fuel celland a catalyst.

2. Description of Related Art

Platinum has often been used as a preferred catalyst material forelectrodes in fuel cells, especially fuel stacks for cars, and inautocatalysts. A catalyst, especially a platinum catalyst is a crucialpart in a fuel cell. The catalytic reaction takes place on the surfaceof the electrodes. The electricity is created by the catalytic reactionwhen a fuel such as Hydrogen is electrochemically oxidized to protons onthe surface of the anode. Platinum is known to be an excellent catalystfor fuel cells; however it is a very expensive material.

Since platinum has a smooth surface and its surface area is limited bythe geometry of the electrode, it is not efficient for transferringelectrical charge. The platinum with a smooth surface is hereinaftercalled shiny platinum.

An electrode which is intended for long term use with a nonrenewableenergy source must require minimal energy—a high electrode capacitanceand correspondingly low electrical impedance is of great importance.

It is known that a catalyst applied on an electrode surface acceleratesthe electrode reactions and that the transfer current is proportional tothe surface area of the electrode. Many attempts are reported trying toimprove the ability of a catalyst converting fuel to electricity. Thoseattempts try to increase the surface area of the electrode withoutincreasing the amount of the expensive platinum catalyst material.

One approach to increase the surface area of a platinum electrodewithout increasing the electrode size is to electroplate platinumrapidly such that the platinum molecules do not have time to arrangeinto a smooth, shiny surface. The rapid electroplating forms a platinumsurface which is commonly known as platinum black. Platinum black has aporous and rough surface which is less dense and less reflective thanshiny platinum. U.S. Pat. No. 4,240,878 to Carter describes a method ofplating platinum black on tantalum.

Platinum black is more porous and less dense than shiny platinum.Platinum black has weak structural and physical strength and istherefore not suitable for applications where the electrode is subjectto even minimal physical stresses. Platinum black also requiresadditives such as lead to promote rapid plating. Finally, due toplatinum black's weak structure, the plating thickness is quite limited.Thick layers of platinum black simply fall apart.

Fuel stacks for cars use about 2 oz of platinum group metals per unit.Pure platinum catalysts are used for hydrogen fueled fuel cells, whilealloys of platinum with ruthenium are typically used for reformedhydrocarbon fuel cells to improve the tolerance of the catalyst tocarbon monoxide.

The fuel cell research estimates that loadings can be reduced to about 1oz per unit through better utilization of platinum and thinnerdeposition layer. Other estimates show that when fuel cells arecommercially produced each engine will require between 0.2 and 0.3 ozplatinum per unit.

The main consumer of world platinum group metal supply is the automobileindustry. 41% of platinum demand in 2001 was accounted for autocatalystuse. Platinum group metals are used in autocatalysts to facilitate theremoval of three of the main combustion byproducts CO, hydrocarbons, andNO_(x). The use of platinum is increased due to strong growth inproduction and sales for diesel cars. Diesel autocatalysts only useplatinum rather than the mixture of platinum and palladium commonly usedin gasoline catalysts.

Platinum is the most common catalyst for fuel cells. However, due to itshigh cost it is often doped with palladium, ruthenium, cobalt, or morerecently iridium or osmium. In addition to its high cost, platinum isalso quite rare. In fact, there is not enough platinum in the world toequip every vehicle in use today with a traditional platinum catalystproton exchange membrane fuel cell. For this reason, there is a highdesire to develop new catalysts, and new platinum deposition techniquesto reduce the amount of platinum needed for fuel cell catalysts andautocatalysts in general.

For the foregoing reasons there is a need for an improved platinumsurface coating and process for coating the surface to obtain anincreased surface area for a given geometry and at the same time thecoating is structurally strong enough to be used in applications wherethe platinum surface coating is subject to physical stresses.

SUMMARY OF THE INVENTION

The present invention is directed in part to a catalyst which comprisesat least one substrate; and a surface coating of said substrate of atleast one of the following metals platinum, palladium or iridium or analloy of two or more metals, or a combination of two or more alloys ormetal layers having an increase in the surface area of 5 times to 500times of the corresponding surface area resulting from the basicgeometric shape.

The present invention is further directed to a fuel cell comprising atleast one catalyst.

The present invention is further directed to a catalyst to facilitatethe removal of three of the main combustion byproducts CO, hydrocarbonsand NO_(x).

The present invention is further directed to an anode and/or a cathodecomprising a substrate wherein the surface coating is electroplated tothe surface of a said conductive substrate at a rate such that theparticles of metal form on the conductive substrate faster thannecessary to form shiny platinum and slower than necessary to formplatinum black.

The present invention is further directed to a method for manufacturingof a catalyst by electroplating a surface coating such that surface hasa rough surface coating comprising electroplating the surface of aconductive substrate at a rate such that the particles are form on theconductive substrate faster than necessary to form shiny platinum andslower than necessary to form platinum black.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a platinum gray surface magnified 2000 times.

FIG. 2 depicts a shiny platinum surface magnified 2000 times.

FIG. 3 depicts a platinum black surface magnified 2000 times.

FIG. 4 depicts color density (D) values and lightness (L*) values forseveral representative samples of platinum gray, platinum black andshiny platinum.

FIG. 5 depicts a three electrode electroplating cell with a magneticstirrer.

FIG. 6 depicts a three electrode electroplating cell in an ultrasonictank.

FIG. 7 depicts a three electrode electroplating cell with a gasdispersion tube.

FIG. 8 depicts an electroplating system with constant voltage control orconstant current control.

FIG. 9 depicts an electroplating system with pulsed current control.

FIG. 10 depicts an electroplating system with pulsed voltage control.

FIG. 11 depicts an electroplating system with scanned voltage control.

FIG. 12 depicts the electrode capacitance for both plated and unplatedelectrodes of varying diameter.

FIG. 13 depicts a representative linear voltage sweep of arepresentative platinum electrode.

FIG. 14 depicts a schematic drawing of a fuel cell.

FIG. 15 depicts a side view of an autocatalyst.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, an illustrative example of a platinum gray surfacecoating for an electrode according to the present invention is shownhaving a fractal surface with a surface area increase of greater than 5times the surface area over that of a shiny platinum surface of the samegeometry, shown in FIG. 2, and an increase in strength over a platinumblack surface, shown in FIG. 3. FIGS. 1 to 3 are images produced on aScanning Electron Microscope at 2000× magnification taken by a JSM5910microscope (JEOL, Tokyo, Japan). Under this magnification level it isobserved that the platinum gray is of a fractal configuration having acauliflower shape with particle sizes ranging from 0.5 μm to 15 μm. Eachbranch of such structure is further covered by smaller and smallerparticles of similar shape. The smallest particles on the surface layermay be in the nanometer range. This rough and porous fractal structureincreases the electrochemically active surface area of the platinumsurface when compared to an electrode with a smooth platinum surfacehaving the same geometric shape.

Because no impurities or other additives such as lead need to beintroduced during the plating process to produce platinum gray, thesurface can be pure platinum. It is very advantageous of not using leadin view of the environment. Lead is likely to lover the catalystactivity in an autocatalyst. This is another advantage of not using anylead in the platinum catalyst. Alternatively, other materials such asiridium, rhodium, gold, tantalum, titanium or niobium could beintroduced during the plating process if so desired but these materialsare not necessary to the formation of platinum gray.

Platinum gray can also be distinguished from platinum black and shinyplatinum by measuring the color of the material on a spectrodensitometerusing the Commission on Illumination L*a*b* color scale.

-   -   L* defines lightness,    -   a* denotes the red/green value, and    -   b*, the yellow/blue value.

The lightness value, called L* Value, can range from 0 to 100, wherewhite is 100 and black is 0— similar to grayscale. The a* value canrange from +60 for red and −60 for green, and the b* value can rangefrom +60 for yellow and −60 for blue. All samples measured have verysmall a* and b* values, they are colorless or in the so called neutralgray zone, which suggests that the lightness value can be used asgrayscale for Platinum coatings.

Another example of a platinum surface coating for an electrode yields arough surface with a surface area increase of greater than 5 times thesurface area for a platinum surface of the same geometry having aregular shape with particle sizes ranging from 0.1 μm to 2.0 μm and hasan average size of 0.4 μm to 0.6 μm, preferably about 0.5 μm. Thethickness of the coating is 0.1 μm to 5.0 μm, preferably 1.0 μm to 4.0μm, more preferably 3.3 μm to 3.8 μm. Some rough features with a scalein the nanometer range were present on each particle. The platedplatinum layer is not believed to be porous. The bead shaped platinumparticles with nanometer rough features on the particles increase theelectrode's electrochemical active surface. The electrochemicalcapacitance of the electrode array with the surface coating of roughplatinum is about 1300 μF/cm² to 1500 μF/cm², measured in a 10 mMphosphate buffered saline solution. The relation of the platinum surfacearea to the thickness of the platinum surface coating is of 4.0 F/cm³ to5.0 F/cm³. The thin-film platinum disks have an average capacitance ofless than 20 μF/cm² before plating, measured at the same condition. Theelectrochemical active surface area increase is 70 to 80, preferablyabout 71 to 75 fold.

The electroplating process with platinum can be preferably performed inan agues solution containing sodium dihydrogen phosphate (NaH₂PO₄)and/or disodium hydrogen phosphate (Na₂HPO₄) and platinum tetra chloride(PtCl₄) at 20° C. to 40° C. Different concentrations of platinum can beused and the range of platinum salt concentrations can be from 1 to 30mM. Other Pt salts will also produce similar results.

Another example of a platinum surface coating yields an electrode havinga rough surface with a surface area increase of greater than 5 times thesurface area for a platinum surface of the same geometry having aregular shape with particle sizes ranging from 0.1 μm to 2.0 μm and hasan average size of 0.4 μm to 0.6 μm, preferably about 0.5 μm. Thethickness of the coating is 0.1 μm to 4.0 μm, preferably 2.0 μm to 3.0μm, more preferably 2.3 μm to 2.8 μm. Some rough features with a scalein the nanometer range were present on each particle. The platedplatinum layer is not believed to be porous. The bead shaped platinumparticles with nanometer rough features on the particles increasedelectrode's electrochemical active surface. The electrochemicalcapacitance of the electrode array with the surface coating of roughplatinum is about 1150 μF/cm² to 1680 μF/cm², measured in a 10 mMphosphate buffered saline solution. The relation of the platinum surfacearea to the thickness of the platinum surface coating is of 5.0 F/cm³ to6.0 F/cm³. The thin-film platinum disks have an average capacitance ofless than 20 μF/cm² before plating, measured at the same condition. Theelectrochemical active surface area increase is 65 to 75, preferablyabout 68 to 72 fold.

The relation of the platinum surface area to the thickness of theplatinum surface coating is of 4.0 F/cm³ to 5.0 F/cm³ as referred to inFIG. 4 and of 5 5.0 F/cm³ to 6.0 F/cm³ as referred to in FIG. 5. FIGS. 4and 5 both depict a rough surface platinum coating according to thepresent invention. This value is calculated by dividing theelectrochemically active platinum surface area (μF/cm³) by the thicknessof the platinum coating (μm). In comparison to the rough surfaceplatinum coating the fractal platinum coating as referred to in FIG. 1has a relation of the platinum surface area to the thickness of theplatinum surface coating of 0.8 F/cm³ to 1.5 F/cm³. The rough platinumcoating of the present invention yields on the same electrochemicallyactive surface area a thinner coating with a higher capacitive volumecompared with platinum gray.

Another example is a palladium surface coating for an electrode having arough surface with a surface area increase of greater than 5 times thesurface area for a palladium surface of the same geometry having aregular shape with particle sizes ranging from 0.1 μm to 3.0 μm,preferably from 0.5 μm to 1.5 μm. The thickness of the coating is 0.1 μmto 5.0 μm, preferably 0.5 μm to 2.0 μm.

Some rough features with a scale in the nanometer range were present oneach particle. The plated palladium layer is not believed to be porous.The bead shaped palladium particles with nanometer rough features on theparticles increase the electrode's electrochemical active surface. Theelectrochemical capacitance of the electrode array with the surfacecoating of rough palladium is about 100 μF/cm² to 300 μF/cm², measuredin a 10 mM phosphate buffered saline solution. The thin-film platinumdisks have an average capacitance of less than 20 μF/cm² before plating,measured at the same condition. The relation of the palladium surfacearea to the thickness of the palladium surface coating is of 1.5 F/cm³to 3.5 F/cm³. The electrochemical active surface area increase is 50 to70, preferably about 52 to 60 fold.

The smallest particles on the surface layer may be in the nanometerrange. This rough structure increases the electrochemically activesurface area of the palladium surface when compared to an electrode witha smooth palladium surface having the same geometric shape.

The surface is pure palladium because no impurities or other additivessuch as lead need to be introduced during the plating process to producethis palladium.

Another example is an iridium surface coating for an electrode having arough surface with a surface area increase of greater than 5 times thesurface area for an iridium surface of the same geometry having anirregular shape with particle sizes ranging from 0.01 μm to 2.0 μm,preferably from 0.1 μm to 1.0 μm. The coating has a thickness from 0.01μm to 10 μm, preferably from 0.8 μm to 3.0 μm.

The plated iridium layer is not believed to be porous. The bead shapediridium particles with nanometer rough features on the particlesincrease the electrode's electrochemical active surface. Theelectrochemical capacitance of the electrode array with the surfacecoating of rough palladium is about 1000 μF/cm² to 1300 μF/cm², measuredin a 10 mM phosphate buffered saline solution. The thin-film platinumdisks have an average capacitance of less than 20 μF/cm² before plating,measured at the same condition. The relation of the palladium surfacearea to the thickness of the palladium surface coating is of 4.5 F/cm³to 6.5 F/cm³. The electrochemical active surface area increase is 55 to70, preferably about 60 to 65 fold. The smallest particles on thesurface layer may be in the nanometer range. This rough structureincreases the electrochemically active surface area of the iridiumsurface when compared to an electrode with a smooth iridium surfacehaving the same geometric shape.

The surface is pure iridium because no impurities or other additivessuch as lead need to be introduced during the plating process to producethis iridium.

The electroplating process with iridium can be preferably performed inan agues solution containing sodium dihydrogen phosphate (NaH₂PO₄)and/or disodium hydrogen phosphate ((Na₂HPO₄) and ammoniumhexachloroiridate ((NH₄)₂IrCl₆) at 20° C. to 40° C. Differentconcentrations of ((NH₄)₂IrCl₆ can be used and the range of iridium saltconcentrations can be from 3 to 30 mM. Other iridium salts such as(NH₄)₃IrCl₆ or IrCl₄ also produce similar, good results.

Referring to FIG. 4, the L*, a*, and b* values for representativesamples of platinum gray, platinum black and shiny platinum are shown asmeasured on a color reflection spectrodensitometer, X-Rite 520. Platinumgray's L* value ranges from 25 to 90, while platinum black and shinyplatinum both have L* values less than 25.

Referring to FIG. 4, color densities have also been measured forrepresentative samples of platinum gray, platinum black and shinyplatinum. Platinum gray's color density values range from 0.4D to 1.3Dwhile platinum black and shiny platinum both have color density valuesgreater than 1.3D.

Platinum gray can also be distinguished from platinum black based on theadhesive and strength properties of the thin film coating of thematerials. Adhesion properties of thin film coatings of platinum grayand platinum black on 500 μm in diameter electrodes have been measuredon a Micro Scratch Tester (CSEM Instruments, Switzerland). A controlledmicro scratch is generated by drawing a spherical diamond tip of radius10 μm across the coating surface under a progressive load from 1millinewton to 100 millinewtons with a 400 μm scratch length. At acritical load the coating will start to fail. Using this test it isfound that platinum gray can have a critical load of over 60millinewtons while platinum black has a critical load of less than 35millinewtons.

Referring to FIGS. 5 to 8, a method to produce platinum gray accordingto the present invention is described comprising connecting a platinumelectrode 2, the anode, and a conductive substrate to be plated 4, thecathode, to a power source 6 with a means of controlling and monitoring8 either the current or voltage of the power source 6. The anode 2,cathode 4, a reference electrode 10 for use as a reference incontrolling the power source and an electroplating solution are placedin an electroplating cell 12 having a means 14 for mixing or agitatingthe electroplating solution. Power is supplied to the electrodes withconstant voltage, constant current, pulsed voltage, scanned voltage orpulsed current to drive the electroplating process. The power source 6is modified such that the rate of deposition will cause the platinum todeposit as platinum gray, the rate being greater than the depositionrate necessary to form shiny platinum and less than the deposition ratenecessary to form platinum black.

Referring to FIGS. 5 to 7, the electroplating cell 12, is preferably a50 ml to 150 ml four neck glass flask or beaker, the common electrode 2,or anode, is preferably a large surface area platinum wire or platinumsheet, the reference electrode 10 is preferably a Ag/AgCl electrode, theconductive substrate to be plated 4, or cathode, can be any suitablematerial depending on the application and can be readily chosen by oneskilled in the art. Preferable examples of the conductive substrate tobe plated 4 include but are not limited to platinum, iridium, rhodium,gold, tantalum, titanium or niobium.

The stirring mechanism is preferably a magnetic stirrer 14 as shown inFIG. 5, an ultrasonic tank 16, such as the VWR Aquasonic SOD, as shownin FIG. 6, or gas dispersion 18 with Argon or Nitrogen gas as shown inFIG. 7. The plating solution is preferably 3 to 30 mM (milimole)ammonium hexachloroplatinate in disodium hydrogen phosphate, but may bederived from any chloroplatinic acid or bromoplatinic acid or otherelectroplating solution. The preferable plating temperature isapproximately in the range of 24° C.-26° C.

Electroplating systems with pulsed current and pulsed voltage controlare shown in FIGS. 9 and 10 respectively. While constant voltage,constant current, pulsed voltage or pulsed current can be used tocontrol the electroplating process, constant voltage control of theplating process has been found to be most preferable. The mostpreferable voltage range to produce platinum gray has been found to bein the range of −0.45 V to −0.85 V. Applying voltage in this range withthe above solution yields a plating rate in the range of about 1 μm perminute to about 0.05 μm per minute, the preferred range for the platingrate of platinum gray. Constant voltage control also allows an array ofelectrodes in parallel to be plated simultaneously achieving a fairlyuniform surface layer thickness for each electrode.

The optimal potential ranges for platinum gray plating are solution andcondition dependent. Linear voltage sweep can be used to determine theoptimal potential ranges for a specific plating system. A representativelinear voltage sweep is shown in FIG. 13. During linear voltage sweep,the voltage of an electrode is scanned cathodically until hydrogen gasstarts developing revealing plating rate control steps of electrontransfer 20 and diffusion 22. For a given plating system, it ispreferable to adjust the electrode potential such that the platinumreduction reaction has a limiting current under diffusion control ormixed control 24 between diffusion and electron transfer but that doesnot result in hydrogen evolution 26.

Furthermore, it has been found that because of the physical strength ofplatinum gray, it is possible to plate surface layers of thicknessgreater than 30 μm. It is very difficult to plate shiny platinum inlayers greater than approximately several microns because the internalstress of the dense platinum layer will cause the plated layer to peeloff and the underlying layers cannot support the above material. Theadditional thickness of the plate's surface layer allows the electrodeto have a much longer usable life.

The following example is illustrative of electroplating platinum on aconductive substrate to form a surface coating of platinum grayaccording to the present invention.

Electrodes with a surface layer of platinum gray are prepared in thefollowing manner using constant voltage plating. An electrode platinumsilicone array having 16 electrodes where the diameter of the platinumdiscs on the array range from 510 to 530 μm is first cleanedelectrochemically in sulfuric acid and the starting electrode impedanceis measured in phosphate buffered saline or acid solution. Referring toFIG. 5, the electrodes are arranged in the electroplating cell such thatthe plating electrode 2 is in parallel with the common electrode 4. Thereference electrode 10 is positioned next to the electrode array 4. Theplating solution is added to the electroplating cell 12 and the stirringmechanism 14 is activated.

A constant voltage is applied on the plating electrode 2 as compared tothe reference electrode 10 using an EG&G PAR M273 potentiostat 6. Theresponse current of the plating electrode 2 is recorded by a recordingmeans 8. The response current is measured by the M273 potentiostat 6.After a specified time, preferably 1 minute-90 minutes, and mostpreferably 30 minutes, the voltage is terminated and the electrode array4 is thoroughly rinsed in deionized water.

The electrochemical impedance of the electrode array 4 with the surfacecoating of platinum gray is measured in a saline or acid solution. Thecharge/charge density and average plating current/current density arecalculated by integrating the area under the plating current vs. timecurve. Energy Dispersed Analysis by X-ray (EDAX™) can be performed onselected electrodes. Scanning Electron Microscope (SEM) Micrographs ofthe plated surface can be taken showing its fractal surface. EnergyDispersed Analysis demonstrates that the sample is pure platinum ratherthan platinum oxide or some other materials.

From this example it is observed that the voltage range is mostdeterminative of the formation of the fractal surface of platinum gray.For this system it observed that the optimal voltage drop across theelectrodes to produce platinum gray is approximately −0.55 to −0.65Volts vs. Ag/AgCl reference electrode. The optimal platinumconcentration for the plating solution is observed to be approximately 8to 18 mM ammonium hexachloroplatinate in 0.4 M (mole) disodium hydrogenphosphate.

FIG. 12 shows the increase in electrode capacitance of severalelectrodes of varying diameter for a polyimide array plated according tothe above example at −0.6 V vs. Ag/AgCl reference electrode for 30minutes compared with unplated electrodes of the same diameters. Becausethe electrode capacitance is proportional to its surface area, thesurface area increase, calculated from electrode capacitance, is 60 to100 times that of shiny platinum for this array. Shiny platinum exhibitssome roughness and has a surface area increase up to 3 times that of thebasic geometric shape. While it is simple to measure a surface areachange between two sample using capacitance, it is difficult to comparea sample with the basic geometric shape.

The present invention provides a very effective method for plating onsmaller substrates by retaining the same or better effectivenesscompared with known plating methods. This method is very useful formanufacturing miniaturized or micro fuel cells especially in theapplications of hand-held electronics and some medical implants.

A change of conditions, including but not limited to the platingsolution, surface area of the electrodes, pH, platinum concentration andthe presence of additives, will also result in change of the optimalcontrolling voltage and/or other controlling parameters according to thebasic electroplating principles. Platinum gray will still be formed solong as the rate of deposition of the platinum particles is slower thanthat for the formation of platinum black and faster than that for theformation of shiny platinum.

A fuel cell 60 is an electrochemical device as shown in FIG. 14 thatcombines hydrogen fuel and oxygen from the air to produce electricity,heat and water. Fuel cells operate without combustion, so they arevirtually pollution free. Since the fuel is converted directly toelectricity, a fuel cell can operate at much higher efficiencies thaninternal combustion engines, extracting more electricity from the sameamount of fuel. The fuel cell itself has no moving parts, which makes ita quiet and reliable source of power.

The fuel cell 60 is composed of an anode 62, which is the negativeelectrode of the fuel cell 60, an electrolyte 64 in the center, whichcan be a liquid or a solid for example a membrane, and a cathode 66which is the positive electrode of the fuel cell 60. As hydrogen flowsinto the fuel cell anode 62, a platinum catalyst in the anodefacilitates the reaction from hydrogen gas into protons and electrons asshown in the equation 1 below.${1.\quad 2\quad H_{2}}\overset{{Pt}_{anode}}{\Rightarrow}{{4\quad H^{+}} + {4{\mathbb{e}}^{-}}}$

The reaction (1) is facilitated by the anode due to the catalyticreaction performed by the electroplated platinum as catalyst. Theelectrons (e⁻) generated in the reaction (1) at the anode 62 flowthrough an external circuit 68 in the form of electric current.

The electrolyte 64 in the center allows only the protons to pass throughthe electrolyte 64 to the cathode 66 side of the fuel cell 60.

As oxygen flows into the fuel cell cathode 66 another platinum catalysthelps the oxygen, protons, and electrons combine to produce pure waterand heat as shown in the equation 2 below.${{2.\quad O_{2}} + {4\quad H^{+}} + {4{\mathbb{e}}^{-}}}\overset{{Pt}_{cathode}}{\Rightarrow}{{2\quad H_{2}O} + \Delta_{heat}}$

The overall chemical reaction which is performed in a fuel cell is shownin the equation 3 below. 3.  2  H₂ + O₂ ⇒ 2  H₂O

Individual fuel cells 60 can be combined into a fuel cell stack toobtain desired amount of electrical power. The number of fuel cells inthe stack determines the total voltage, while the surface area of thecell determines its current.

According to the present invention platinum gray can be applied byelectroplating for the coating of the anode 62 and cathode 66. Platinumgray provides an enlarged service area by applying less platinum for thecoating and an improved adhesion to the substrate of the electrode.Platinum gray has the same or improved performance of the fuel cell 60and at the same time a large amount of platinum can be saved. The fuelcell production is economical and ecological by using platinum gray forthe coating of the anode 62 and the cathode 66.

A catalyst, especially an autocatalyst 70 is a cylinder of circular orelliptical cross section as shown in FIG. 15, made from ceramic or metalformed into a fine honeycomb and coated with a solution of chemicals andplatinum group metals. It is mounted inside a stainless catalyticconverter, and is installed in the exhaust line of the vehicle betweenthe engine and a small muffler. Vehicle exhaust contains a number ofharmful elements which can be controlled by the platinum group metals inautocatalysts.

The major exhaust pollutants are carbon monoxide, which is a poisonousgas, oxides of nitrogen, which contribute to acid rain, low level ozoneand smog formation and which exacerbate breathing problems,hydrocarbons, which are involved in the formation of smog and have anunpleasant smell, and particulate, which contains known cancer causingcompounds.

Autocatalysts convert over 90 percent of hydrocarbons as shown in theequation 4 below:${4.\quad{CH}_{4}} + {2\quad{O_{2}\overset{{Pt}_{catalyst}}{\Longrightarrow}\quad{CO}_{2}}} + \quad{2\quad H_{2}O}$carbon monoxide as shown in the equation 5 below:${5.\quad 2\quad{CO}} + {{O_{2}\overset{{Pt}_{catalyst}}{\Longrightarrow}2}\quad{CO}_{2}}$oxides of nitrogen from gasoline engines as shown in equations 6 and 7below:${6.\quad 2\quad{{NO}_{2}\overset{{Pt}_{catalyst}}{\Longrightarrow}N_{2}}} + {2\quad O_{2}}$${7.\quad 2\quad{{NO}_{3}\overset{{Pt}_{catalyst}}{\Longrightarrow}N_{2}}} + {3\quad O_{2}}$and ozone as shown in equation 8 below:$8.\quad 2\quad{O_{3}\overset{{Pt}_{catalyst}}{\Longrightarrow}\quad 3}\quad O_{2}$into less harmful carbon dioxide, nitrogen, water vapor and oxygen asshown above in the equations 3 to 7.

The dominant material of ceramic substrate for catalytic converters isporous cordierite, which can be used at temperatures up to 1300° C.Because of its nature of crystallization, chemical composition,cordierite has an extremely low thermal expansion coefficient. A lowpressure drop, chemical inertness, fast heat up time, and structuralstability at high temperatures make a ceramic honeycomb an idealcatalyst substrate for both oxidation and reduction catalysts.

According to the present invention metal can be applied byelectroplating for the coating of the inside of a cylinder of circularor elliptical cross section made from ceramic or metal. Metal appliedaccording to the present invention provides an enlarged surface area byapplying less platinum for the coating and an improved adhesion to thesubstrate of the catalyst. Metal of the present invention has the sameor improved performance of the catalyst. At the same time a large amountof metal, like platinum, palladium, or iridium can be saved. Thecatalyst production is economical and ecological by using metal of thepresent invention for the coating of the catalyst substrate.

The present invention will be further explained in detail by thefollowing examples.

EXAMPLE 1 Electroplating Palladium on a Conductive Substrate PalladiumPlating Solution Preparation

2.7 g sodium dihydrogen phosphate (NaH₂PO₄) and 3.2 g disodium hydrogenphosphate (Na₂HPO₄) [Fluka] were dissolved in 100 ml deionized water,and stirred by magnetic stirring for 30 minutes. The concentrations forNaH₂PO₄ and Na₂HPO₄ were equally 225 mM. Then 0.18 g Palladium chloride(PdCl₂) [Aldrich] was added to the phosphate solution. The solution wasthen stirred for 30 minutes and filtered to black solids. The PdCl₂concentration was about 5 mM. The pH of the solution was measured at6.8. The color of the solution was brown. The solution was deaeratedbefore the plating process by bubbling nitrogen through the solution.

Preparation of the Substrate

A thin-film platinum polyimide array was used for palladium plating. Thearray included 16 electrodes with 200 μm thin-film Pt disk as exposedelectrode surface. All the electrodes in the array were shorted tocommon contact points for the plating. The Pt disk electrodes were firstelectrochemically cleaned by bubbling the surface with oxygen at +2.8Vvs Ag/AgCl in 0.5 M H₂SO₄ for 10 sec. Then the surface was cleaned bybubbling with hydrogen at −1.2 V vs Ag/AgCl in 0.5 M H₂SO₄ for 15 sec.This removes surface contaminations and polymer residues.

Electroplating Cell

A classical Pyrex glass three-electrode reaction cell was used for theelectroplating. The reference electrode compartment was separated fromthe reaction compartment by a Vicor porous frit, in order to avoid themigration of concentrated KCl and AgCl from the inner filling solutionof the reference electrode to the plating bath. The counter electrodewas a platinized-platinum sheet of a real surface area equal to 1.8 cm².

A digital magnetic stirrer (Dataplate PMC720) was used to agitate thesolution during plating. The solution temperatures were from 15° C. to80° C. and were controlled by a VWR circulating water bath with adigital temperature controller (VWR 1147P).

The potential was controlled by using an EG&G PARC model 273potentiostat-galvanostat and the response current, current density andcharge were recorded by EG&G PARC M270 software. The charge/chargedensity and average plating current/current density were calculated byintegrating the area under the plating current vs. time curve. Theplating time was from 1 minute to 120 minutes.

Palladium Plating

A platinum polyimide electrode array having 16 electrodes (FIG. 14)having a diameter of 200 μm platinum disc on the array was cleanedelectrochemically in 0.5 M H₂SO₄. The electrode array was placed in anelectroplating cell containing a plating solution having a concentrationof 5 mM palladium chloride in 0.025 M sodium dihydrogen phosphate and0.425 M disodium hydrogen phosphate. The plating bath temperature was at22° C. A constant voltage of −1.0 V vs Ag/AgCl reference electrode wasapplied on the electrode and terminated after 10 minutes. The electrodearray was thoroughly rinsed in deionized water. The charge/chargedensity and average plating current/current density were calculated byintegrating the area under the plating current vs. time curve. Thecurrent density was near linearly increased from initial 0.96 A/cm² tofinal 3.5 A/cm². The electrochemical capacitance of the electrode arraywith the surface coating of rough palladium was 190 μF/cm², measured ina 10 mM phosphate buffered saline solution. The smooth thin-film Ptdisks measured at the same condition before plating an averagecapacitance of less than 20 μF/cm². The electrochemical active surfacearea increase is about 10 fold in this case. The optimal voltage dropacross the electrodes for producing rough iridium was from −0.8 to −1.3Volts vs. Ag/AgCl reference electrode. The plated palladium surfacecoating thickness was about 1.0 μm.

Example 1 yields a palladium surface coating having a rough surface asshown in FIG. 4. The electrochemical active surface area increase isabout 10 fold. The relation of surface area to the thickness of theplatinum surface coating is 1.90 F/cm³ [surface coating of roughplatinum 190 μF/cm² per thickness of the platinum coating of 1.0 μm.]The palladium surface coating adhesive strength was 54 mN. The palladiumcoating contains particles with very regular particle shape and regularaverage size. The coating is thinner than known coatings and has a roughsurface which is mainly not porous with a large surface area. Thecoating provides a good adherence between the substrate and the platinumcoating. The palladium coated electrode is biocompatible and thereforeimplantable and provides less tissue reaction.

EXAMPLE 2 Electroplating Iridium on a Conductive Substrate IridiumPlating Solution Preparation

0.3 g sodium dihydrogen phosphate (NaH₂PO₄) and 6.03 g disodium hydrogenphosphate (Na₂HPO₄) [Fluka] were dissolved in 100 ml deionized water,magnetic stirring for 30 minutes. The concentrations for NaH₂PO₄ andNa₂HPO₄ were 25 mM and 425 mM, respectively. Then 0.882 g of Ammoniumhexachloroiridate ((NH₄)₂IrCl₆) from [Alfa Aesar] was added to thephosphate solution to form the iridium salt concentrations of 20 mM. Thesolution was stirred for 30 minutes prior to plating. The pH of thesolution was measured at 7.9. The initial color of the solution is brownand changed to dark blue after overnight aging.

Preparation of the Substrate

A thin-film platinum polyimide array was used for iridium plating. Thearray had 16 electrodes with 200 μm thin-film Pt disk as exposedelectrode surface. All electrodes in the array were shorted to a commoncontact points for the plating. The Pt disk electrodes were firstelectrochemically cleaned by bubbling the surface with oxygen at +2.8 Vvs Ag/AgCl in 0.5 M H₂SO₄ for 10 sec. Then the surface was cleaned bybubbling with hydrogen at −1.2 V vs Ag/AgCl in 0.5 M H₂SO₄ for 15 sec.This removes surface contaminations and polymer residues.

Electroplating Cell

A classical Pyrex glass three-electrode reaction cell was used for theelectroplating. The reference electrode compartment was separated fromthe reaction compartment by a Vicor porous frit, in order to avoid themigration of concentrated KCl and AgCl from the inner filling solutionof the reference electrode to the plating bath. The counter electrodewas a platinized-platinum sheet of a real surface area equal to 1.8 cm².

A digital magnetic stirrer (Dataplate PMC720) was used to agitate thesolution during plating. The solution temperatures were from 15° C. to80° C. and were controlled by a VWR circulating water bath with adigital temperature controller (VWR 1147P).

The potential was controlled by using an EG&G PARC model 273potentiostat-galvanostat and the response current, current density andcharge were recorded by EG&G PARC M270 software. The charge/chargedensity and average plating current/current density were calculated byintegrating the area under the plating current vs. time curve. Theplating time was from 1 minute to 120 minutes.

Iridium Plating

A platinum polyimide electrode array having 16 electrodes (FIG. 14)having a diameter of 200 μm platinum disc on the array was cleanedelectrochemically in 0.5 M H₂SO₄. The electrode array was placed in anelectroplating cell containing a plating solution having a concentrationof 28 mM ammonium hexachloroiridate in 0.025 M sodium dihydrogenphosphate and 0.425 M disodium hydrogen phosphate. The plating bathtemperature was at 32° C. A constant voltage of −2.5 V vs Ag/AgClreference electrode was applied on the electrode and terminated after 60minutes. The electrode array was thoroughly rinsed in deionized water.The charge/charge density and average plating current/current densitywere calculated by integrating the area under the plating current vs.time curve. The current density was near linearly increased from initial1.6 A/cm² to final 2.2 A/cm². The electrochemical capacitance of theelectrode array with the surface coating of rough iridium was 1115μF/cm², measured in a 10 mM phosphate buffered saline solution. Thethin-film Pt disks measured before plating at the same conditions anaverage capacitance of lower than 20 μF/cm². The electrochemical activesurface area increase is about 56 fold in this case. The optimal voltagedrop across the electrodes for producing rough iridium was from −1.5 to−3.0 Volts vs. Ag/AgCl reference electrode. The plated iridium surfacecoating thickness was about 2.0 μm. The electrochemical active surfacearea increase is about 56 fold. The relation of surface area to thethickness of the iridium surface coating is 5.58 F/cm³ [surface coatingof rough iridium 1115 μF/cm² per thickness of the iridium coating of 2.0μm.] The platinum surface coating adhesive strength was 62 mN.

Example 2 yields an iridium surface coating having a rough surface asshown in FIG. 5. The iridium coating contains particles with veryregular particle shape and regular average size. The coating is thinnerthan known coatings and has a rough surface which is mainly not porouswith a large surface area. The coating provides a good adherence betweenthe substrate and the coating. The iridium coated electrode isbiocompatible and therefore implantable and provides less tissuereaction.

EXAMPLE 3 Electroplating Platinum on a Conductive Substrate PlatinumPlating Solution Preparation

0.3 g sodium dihydrogen phosphate (NaH₂PO₄) and 6.03 g disodium hydrogenphosphate (Na₂HPO₄) [Fluka] were dissolved in 100 ml deionized water,and stirred by magnetic stirring for 30 minutes. The concentrations forNaH₂PO₄ and Na₂HPO₄ were 25 mM and 425 mM. Then 0.5 g of Platinumchloride (PtCl₄) [Alfa Aesar] was added to the phosphate solution toform the platinum salt concentrations of 15 mM. The solution was thenstirred for 30 minutes. Different concentrations of (PtCl₄) were used inthe experiments and the range of Pt salt concentrations was from 3 to 30mM. The pH of the solution was measured at 7.9. The color of thesolution was amber. The solution was deaerated before the platingprocess by bubbling nitrogen through the solution.

Preparation of the Substrate

A thin-film platinum polyimide array was used for platinum plating. Thearray included 16 electrodes with 200 μm thin-film Pt disk as exposedelectrode surface. All the electrodes in the array were shorted tocommon contact points for the plating. The Pt disk electrodes were firstelectrochemically cleaned by bubbling the surface with oxygen at +2.8Vvs Ag/AgCl in 0.5 M H₂SO₄ for 10 sec. Then the surface was cleaned bybubbling with hydrogen at −1.2 V vs Ag/AgCl in 0.5 M H₂SO₄ for 15 sec toremove surface contaminations and polymer residues.

Electroplating Cell

A classical Pyrex glass three-electrode reaction cell was used for theelectroplating. The reference electrode compartment was separated fromthe reaction compartment by a Vicor porous frit, in order to avoid themigration of concentrated KCl and AgCl from the inner filling solutionof the reference electrode to the plating bath. The counter electrodewas a platinized-platinum sheet of a real surface area equal to 1.8 cm².

A digital magnetic stirrer (Dataplate PMC720) was used to agitate thesolution during plating. The solution temperatures were from 15° C. to80° C. and were controlled by a VWR circulating water bath with adigital temperature controller (VWR 1147P).

The potential was controlled by using an EG&G PARC model 273potentiostat-galvanostat and the response current, current density andcharge were recorded by EG&G PARC M270 software. The charge/chargedensity and average plating current/current density were calculated byintegrating the area under the plating current vs. time curve. Theplating time was from 1 minute to 60 minutes.

Platinum Plating

A platinum polyimide electrode array having 16 electrodes (FIG. 14)having a diameter of 200 μm platinum disc on the array was cleanedelectrochemically in 0.5 M H₂SO₄. The electrode array was placed in anelectroplating cell containing a plating solution having a concentrationof 15 mM platinum chloride in 0.025 M sodium dihydrogen phosphate and0.425 M disodium hydrogen phosphate. The plating bath temperature was at22° C. A constant voltage of −0.525 V vs Ag/AgCl reference electrode wasapplied on the electrode and terminated after 10 minutes. The electrodearray was thoroughly rinsed in deionized water. The charge/chargedensity and average plating current/current density were calculated byintegrating the area under the plating current vs. time curve. Thecurrent density was near linearly increased from initial 11.1 A/cm² tofinal 15.2 A/cm². The electrochemical capacitance of the electrode arraywith the surface coating of rough platinum was 1462 μF/cm², measured ina 10 mM phosphate buffered saline solution. The thin-film Pt disks onlyhave an average capacitance of less than 20 μF/cm² before platingmeasured at the same condition. The optimal voltage drop across theelectrodes for producing rough platinum was from −0.4 to −0.7 Volts vs.Ag/AgCl reference electrode. The plated platinum surface coatingthickness is about 3.5 μm. The electrochemical active surface areaincrease is about 73 fold. The relation of surface area to the thicknessof the platinum surface coating is 4.18 F/cm³ [surface coating of roughplatinum 1462 μF/cm² per thickness of the platinum coating of 3.5 μm.]The platinum surface coating adhesive strength was 55 mN.

The platinum coating contains particles with very regular particle shapeand regular average size. The coating is thinner than known platinumcoatings and has a rough surface which is mainly not porous with a largesurface area. The coating provides a good adherence between thesubstrate and the platinum coating. The platinum coated electrode isbiocompatible and therefore implantable and provides less tissuereaction.

EXAMPLE 4 Electroplating Platinum on a Conductive Substrate PlatinumPlating Solution Preparation

0.3 g sodium dihydrogen phosphate (NaH₂PO₄) and 6.03 g disodium hydrogenphosphate (Na₂HPO₄) [Fluka] were dissolved in 100 ml deionized water,and stirred by magnetic stirring for 30 minutes. The concentrations forNaH₂PO₄ and Na₂HPO₄ were 25 mM and 425 mM. Then 0.5 g of Platinumchloride (PtCl₄) [Alfa Aesar] was added to the phosphate solution toform the platinum salt concentrations of 15 mM. The solution was thenstirred for 30 minutes and filtered to black solids. Differentconcentrations of (PtCl₄) were used in the experiments and the range ofPt salt concentrations was from 3 to 30 mM. The pH of the solution wasmeasured at 7.9. The color of the solution was amber. The solution wasdeaerated before the plating process by bubbling nitrogen through thesolution.

Preparation of the Substrate

A thin-film platinum polyimide array was used for platinum plating. Thearray included 16 electrodes with 200 μm thin-film Pt disk as exposedelectrode surface. All the electrodes in the array were shorted tocommon contact points for the plating. The Pt disk electrodes were firstelectrochemically cleaned by bubbling the surface with oxygen at +2.8Vvs Ag/AgCl in 0.5 M H₂SO₄ for 10 sec. Then the surface was cleaned bybubbling with hydrogen at −1.2 V vs Ag/AgCl in 0.5 M H₂SO₄ for 15 sec toremove surface contaminations and polymer residues.

Electroplating Cell

A classical Pyrex glass three-electrode reaction cell was used for theelectroplating. The reference electrode compartment was separated fromthe reaction compartment by a Vicor porous frit, in order to avoid themigration of concentrated KCl and AgCl into the inner filling solutionof the reference electrode. The counter electrode was aplatinized-platinum sheet of a real surface area equal to 1.8 cm².

A digital magnetic stirrer (Dataplate PMC720) was used to agitate thesolution during plating. The solution temperatures were from 15° C. to80° C. and were controlled by a VWR circulating water bath with adigital temperature controller (VWR 1147P).

The potential was controlled by using an EG&G PARC model 273potentiostat-galvanostat and the response current, current density andcharge were recorded by EG&G PARC M270 software. The charge/chargedensity and average plating current/current density were calculated byintegrating the area under the plating current vs. time curve. Theplating time was from 1 minute to 60 minutes.

Platinum Plating

A platinum polyimide electrode array having 16 electrodes (FIG. 14)having a diameter of 200 μm platinum disc on the array was cleanedelectrochemically in 0.5 M H₂SO₄. The electrode array was placed in anelectroplating cell containing a plating solution having a concentrationof 15 mM platinum chloride in 0.025 M sodium dihydrogen phosphate and0.425 M disodium hydrogen phosphate. The plating bath temperature was at22° C. A constant voltage of −0.5 V vs Ag/AgCl reference electrode wasapplied on the electrode and terminated after 10 minutes. The electrodearray was thoroughly rinsed in deionized water. The charge/chargedensity and average plating current/current density were calculated byintegrating the area under the plating current vs. time curve. Thecurrent density was near linearly increased from initial 10.8 A/cm² tofinal 14.6 A/cm². The electrochemical capacitance of the electrode arraywith the surface coating of rough platinum was 1417 μF/cm², measured ina 10 mM phosphate buffered saline solution. The thin-film Pt disks onlyhave an average capacitance of less than 20 pF/cm² before platingmeasured at the same condition. The optimal voltage drop across theelectrodes for producing rough platinum was from −0.4 to −0.7 Volts vs.Ag/AgCl reference electrode. The plated platinum surface coatingthickness is about 2.5 μm. The electrochemical active surface areaincrease is about 70 fold. The relation of surface area to the thicknessof the platinum surface coating is 5.67 F/cm³ [surface coating of roughplatinum 1417 μF/cm² per thickness of the platinum coating of 2.5 μm.]The platinum surface coating adhesive strength was 58 mN.

The platinum coating contains particles with very regular particle shapeand regular average size. The coating is thinner than known platinumcoatings and has a rough surface which is mainly not porous with a largesurface area. The coating provides a good adherence between thesubstrate and the platinum coating. The platinum coated electrode isbiocompatible and therefore implantable and provides less tissuereaction.

EXAMPLE 5 Electroplating Platinum Gray on a Conductive Substrate

A platinum polyimide electrode array having 16 electrodes (FIG. 14)having a diameter of 200 μm platinum disc on the array was cleanedelectrochemically in 0.5 M H₂SO₄. The electrode array was placed in anelectroplating cell containing a plating solution having a concentration20 mM ammonium hexachloroplatinate, 0.025 M sodium dihydrogen phosphateand 0.425 M disodium hydrogen phosphate. The voltage of −0.65 V wasterminated after 30 minutes. The electrode was thoroughly rinsed indeionized water. The electrochemical capacitance of the electrode withthe surface coating of platinum gray was 1200 μF/cm², measured in a 10mM phosphate buffered saline solution. The charge/charge density andaverage plating current/current density were calculated by integratingthe area under the plating current vs. the time curve. The optimalvoltage drop across the electrodes for producing platinum gray was from−0.55 to −0.75 Volts vs. Ag/AgCl reference electrode.

The platinum coating showed the following properties:

-   -   platinum surface coating thickness: 11.0 μm;    -   electrochemical active surface area increase: 60 fold;    -   platinum surface coating adhesive strength: 50 mN; and    -   platinum surface coating color density: 1.0 D.

Example 5 yields a platinum surface coating having a fractal surface asshown in FIG. 1. The relation of surface area to the thickness of theplatinum surface coating is 1.09 F/cm³ [surface coating of roughplatinum 1200 μF/cm² per thickness of the platinum coating of 11.0 μm.]The coating provides a good adherence between the substrate and theplatinum coating. The platinum coated electrode is biocompatible andtherefore implantable and provides less tissue reaction.

The plating conditions and properties of the platinum coatings performedin Examples 1 to 5 are summarized in the following tables 1 to 3. TABLE1 Conditions of the Plating Reactions Conditions Plating Agent Temp.Voltage Time Example 1  5 mM PdCl₂ 22° C. −1.0 V 10 min Rough Pd Example2 28 mM NH₄[PtIr₆] 32° C. −2.5 V 60 min Rough Ir Example 3 15 mM PtCl₄22° C. −0.525 V  10 min Rough Pt Example 4 15 mM PtCl₄ 22° C. −0.5 V 10min Rough Pt Example 5 20 mM NH₄[PtCl₆] 22° C. −0.6 V 30 min Fractal Pt

TABLE 2 Properties of the Coatings Final Area Coating/ PropertiesCapacitance Thickness Increase Thickness Example 1  190 μF/cm² 1.0 μm 10fold 1.90 F/cm³ Rough Pd Example 2 1115 μF/cm² 2.0 μm 56 fold 5.58 F/cm³Rough Ir Example 3 1462 μF/cm² 3.5 μm 73 fold 4.18 F/cm³ Rough PtExample 4 1417 μF/cm² 2.5 μm 70 fold 5.67 F/cm³ Rough Pt Example 5 1200μF/cm² 11.0 μm  60 fold 1.09 F/cm³ Fractal Pt

TABLE 3 Properties of the Coatings Adhesive Current Density Voltage DropAcross the Properties Strength Initial to Final Electrodes Example 1 54mN 0.96 A/cm² to −0.8 V to −1.3 V Rough Pd  3.5 A/cm² Example 2 60 mN 1.6 A/cm² to −1.5 V to −3.0 V Rough Ir  2.2 A/cm² Example 3 55 mN 11.1A/cm² to −0.4 V to −0.7 V Rough Pt 15.2 A/cm² Example 4 58 mN 10.8 A/cm²to −0.4 V to −0.7 V Rough Pt 14.6 A/cm² Example 5 50 mN 15.1 A/cm² to−0.55 V to −0.75 V Fractal Pt 24.5 A/cm²

While the invention has been described by means of specific embodimentsand applications thereof, it is understood that numerous modificationsand variations could be made thereto by those skilled in the art withoutdeparting from the spirit and scope of the invention. It is therefore tobe understood that within the scope of the claims, the invention may bepracticed otherwise than as specifically described herein.

1. A catalyst comprising: at least one substrate; and a surface coatingof said substrate of at least one of the following metals platinum,palladium or iridium or an alloy of two or more metals, or a combinationof two or more alloys or metal layers having an increase in the surfacearea of 5 times to 500 times of the corresponding surface area resultingfrom the basic geometric shape.
 2. The catalyst of claim 1 wherein saidsurface coating has a surface area of 50 times to 200 times thecorresponding surface area resulting from the basic geometric shape. 3.The catalyst of claim 1 wherein said surface coating has a thickness ofat least 1 micron.
 4. The catalyst of claim 1 wherein said surfacecoating has an adhesive strength as measured by critical load greaterthan 35 millinewtons.
 5. A fuel cell comprising at least one catalyst ofclaim
 1. 6. A micro fuel cell according to the fuel cell of claim
 5. 7.An autocatalyst comprising at least one catalyst of claim
 1. 8. An anodeand/or a cathode comprising a substrate wherein the surface coating iselectroplated to the surface of said conductive substrate at a rate suchthat the metal particles form on the conductive substrate faster thannecessary to form shiny platinum and slower than necessary to formplatinum black.
 9. A method for manufacturing of a catalyst byelectroplating a surface coating such that surface has a rough surfacecoating comprising: electroplating the surface of a conductive substrateat a rate such that the particles are form on the conductive substratefaster than necessary to form shiny platinum and slower than necessaryto form platinum black.
 10. The method of claim 9 wherein said step ofelectroplating is accomplished at a rate of more than 0.05 microns perminute, but less than 1 micron per minute.
 11. The method of claim 9wherein said electroplating is accomplished at a rate of greater orequal to 1 micron per minute, but less than 10 microns per minute. 12.The method of claim 9 wherein said electroplating is controlled by theelectrode voltage.
 13. The method of claim 12 wherein said voltage is aconstant voltage.
 14. The method of claim 12 wherein the controlledvoltage causes at least a partially diffusion limited plating reaction.15. The method of claim 9 wherein the voltage of said electroplating isless than 0.2 Volts and greater than −1 Volts vs. Ag/AgCl referenceelectrode.
 16. The method of claim 9 wherein the electroplating solutionis at least 3 mM but less than 30 mM ammonium hexachloroplatinate inabout 0.4 M disodium hydrogen phosphate.
 17. A method of using at leastone catalyst of claim 1 in a fuel cell.
 18. A method of using at leastone catalyst of claim 1 in an autocatalyst.